I am working with a data Adult
that I have changed and would like to save it as a csv. however after saving it as a csv and re-loading the data to work with again, the data is not converted properly. The headers are not preserved and some columns are now combined. I have looked through the page and online, but what I have tried is not working. I load the data in with the following code:
import numpy as np ##Import necassary packages
import pandas as pd
import matplotlib.pyplot as plt
from pandas.plotting import scatter_matrix
from sklearn.preprocessing import *
url2="http://archive.ics.uci.edu/ml/machine-learning-databases/adult/adult.data" #Reading in Data from a freely and easily available source on the internet
Adult = pd.read_csv(url2, header=None, skipinitialspace=True) #Decoding data by removing extra spaces in cplumns with skipinitialspace=True
##Assigning reasonable column names to the dataframe
Adult.columns = ["age","workclass","fnlwgt","education","educationnum","maritalstatus","occupation",
"relationship","race","sex","capitalgain","capitalloss","hoursperweek","nativecountry",
"less50kmoreeq50kn"]
After inserting missing values and changing the data frame as desired I have tried:
df = Adult
df.to_csv('file_name.csv',header = True)
df.to_csv('file_name.csv')
and a few other variations. How can I save the file to a CSV and preserve the correct format for the next time I read the file in?
When re-loading the data I use the code:
import pandas as pd
df = pd.read_csv('file_name.csv')
when running df.head
the output is:
<bound method NDFrame.head of Unnamed: 0 Unnamed: 0.1 age ... Black Asian-Pac-Islander Other
0 0 0 39 ... 0 0 0
1 1 1 50 ... 0 0 0
2 2 2 38 ... 0 0 0
3 3 3 53 ... 1 0 0
and print(df.loc[:,"age"].value_counts())
the output is:
36 898
31 888
34 886
23 877
35 876
which should not have 2 columns
If you pickle it like so:
Adult.to_pickle('adult.pickle')
You will, subsequently, be able to read it back in using read_pickle as follows:
original_adult = pd.read_pickle('adult.pickle')
Hope that helps.
If you want to preserve the output column order you can specify the columns directly while saving the DataFrame:
import pandas as pd
url2 = "http://archive.ics.uci.edu/ml/machine-learning-databases/adult/adult.data"
df = pd.read_csv(url2, header=None, skipinitialspace=True)
my_columns = ["age", "workclass", "fnlwgt", "education", "educationnum", "maritalstatus", "occupation",
"relationship","race","sex","capitalgain","capitalloss","hoursperweek","nativecountry",
"less50kmoreeq50kn"]
df.columns = my_columns
# do the computation ...
df[my_columns].to_csv('file_name.csv')
You can add parameter index=False
to the to_csv('file_name.csv', index=False)
function if you are not interested in saving the DataFrame row index. Otherwise, while reading the csv file again you'd need to specify the index_col
parameter.
According to the documentation value_counts()
returns a Series
object - you see two columns because the first one is the index - Age (36, 31, ...), and the second is the count (898, 888, ...).
I replicated your code and it works for me. The order of the columns is preserved.
Let me show what I tried. Tried this batch of code:
import numpy as np ##Import necassary packages
import pandas as pd
import matplotlib.pyplot as plt
from pandas.plotting import scatter_matrix
from sklearn.preprocessing import *
url2="http://archive.ics.uci.edu/ml/machine-learning-
databases/adult/adult.data" #Reading in Data from a freely and easily
available source on the internet
Adult = pd.read_csv(url2, header=None, skipinitialspace=True) #Decoding data
by removing extra spaces in cplumns with skipinitialspace=True
##Assigning reasonable column names to the dataframe
Adult.columns =["age","workclass","fnlwgt","education","educationnum","maritalstatus","occupation",
"relationship","race","sex","capitalgain","capitalloss","hoursperweek","nativecountry",
"less50kmoreeq50kn"]
This worked perfectly. Then
df = Adult
This also worked. Then I saved this data frame to a csv file. Make sure you are providing the absolute path to the file even if is is being saved in the same folder as this script.
df.to_csv('full_path_to_the_file.csv',header = True)
# so someting like
#df.to_csv('Users/user_name/Desktop/folder/NameFile.csv',header = True)
Load this csv file into a new_df. It will generate a new column for keeping track of index. It is unnecessary and you can drop it like following:
new_df = pd.read_csv('Users/user_name/Desktop/folder/NameFile.csv', index_col = None)
new_df= new_df.drop('Unnamed: 0', axis =1)
When I compare the columns of the new_df from the original df, with this line of code
new_df.columns == df.columns
I get
array([ True, True, True, True, True, True, True, True, True,
True, True, True, True, True, True])
You might not have been providing the absolute path to the file or saving the file twice as here. You only need to save it once.
df.to_csv('file_name.csv',header = True)
df.to_csv('file_name.csv')
When you save the dataframe in general, the first column is the index, and you sould load the index when reading the dataframe, also whenever you assign a dataframe to a variable make sure to copy the dataframe:
df = Adult.copy()
df.to_csv('file_name.csv',header = True)
And to read:
df = pd.read_csv('file_name.csv', index_col=0)
The first columns from print(df.loc[:,"age"].value_counts())
is the index column which is shown if you query the datframe, to save this to a list, use the to_list
method:
print(df.loc[:,"age"].value_counts().to_list())
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